Managed Watercourses Help Maintain Water Vole Populations

Water vole populations in managed watercourses are bucking the national trend and showing strong and stable populations, against evidence of decline in other areas across the UK.

A study published earlier this summer by the Mammal Society and Natural England, found water vole populations in the UK had declined by almost 70% in the last 20 years, putting them on the endangered list. Factors such as loss of habitat, disease, predation by the non-native North American mink, urban development, and use of pesticides may all be to blame, the report said.

Water vole

Water vole

However, local research undertaken across various locations in the Fens, has demonstrated stable populations in watercourses managed by the local water level management authority, the Middle Level Commissioners.

Responsible for the provision of flood defence and water level management within an area encompassing parts of Cambridgeshire and West Norfolk, the Middle Level Commissioners also have conservation duties to fulfil when undertaking their functions.

Water voles are one of the key species on drains and other waterways within the Middle Level. Despite the reduction in their distribution country-wide, the Fens have remained a stronghold for water voles, and the Middle Level has one of the largest populations spread along 620 miles of ditches, drains and rivers.

Several different surveys of water voles have been carried out by the Bedfordshire, Cambridgeshire and Northamptonshire Wildlife Trust, and Anglian Water with the Middle Level area. The most recent, in 2015, confirmed the results of earlier surveys that ditches managed by internal drainage boards within the Middle Level had high levels of occupancy by water vole, with 93% of IDB maintained drains surveyed showing evidence of the presence of water voles.

The survey found that the cleaning out of drains on a regular basis does not have a significant effect on water vole populations, in fact those that had been cleansed in the past four years, actually had stronger populations.

“It promotes the growth of a diverse selection of young water plants,” explains Peter Beckenham, conservation officer at Middle Level Commissioners. “It provides the age and variety of vegetation they prefer.

“Typically, we see water voles move around our drainage districts, and generally return to managed areas around one year after drains have been cleaned.”

Innes Thomson, chief executive of the Association of Drainage Authorities (ADA), the representative body for drainage, water level and flood risk management authorities, comments, “IDBs invest significantly in both maintaining the conveyance and capacity of watercourses to reduce flood risk, and habitat preservation and creation for aquatic species such as the water vole. It is a careful balancing act and the Middle Level is a clear illustration of coalescing water level management requirements with environmental responsibilities, a commitment mirrored by IDBs around the country.”


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